Why slopes seem steeper than they are when gazed at

Published: Friday, February 11, 2011, 17:55 [IST]

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Washington, Feb 11 (ANI): Scientists have finally found that our perception of climbing or descending hills being dangerous is because our view is clouded by the expected physical exertion or danger of traversing it.

For more than a decade, researchers thought that our judgment was biased by our fatigue or fear of falling, said Dennis Shaffer, associate professor of psychology at Ohio State University's Mansfield campus.

Shaffer and then-undergraduate student Mariagrace Flint uncovered a contradiction, when they compared how we perceive the angle of stairs versus escalators.

"We found that people tend to overestimate a slant even when they are looking at an escalator, and climbing or descending it would require practically no effort at all," said Shaffer.

For the study, 200 passers-by were asked to judge the angle of a set of stairs on the Mansfield campus, while another 200 were asked to judge the angle of an escalator in a Mansfield Sears store.

In each case, 100 people viewed the angle from the top, and 100 from the bottom.

On average, people consistently overestimated the slant by 18-19 degrees, regardless of whether they were looking at a set of stairs or an escalator, from the top or from the bottom.

The actual slope of the steps was 25 degrees, and the slope of the escalator was 30 degrees, but people judged them to be an average of 44 degrees and 48 degrees, respectively.

"In fact, their overestimates were virtually identical," said Shaffer.

The study adds to a growing body of evidence that body-based factors, such as climbing effort or perceived danger, do not have the strong influences on our perception of slant that researchers once thought.

At least, Shaffer added, we can take comfort that our misperceptions are consistent.

He suspects that our perception of slant is biased by a more basic misperception: the angle of our gaze.

People, he said, tend to think they are looking downward at a sharper angle than they actually are.

The study is published in the current issue of the journal Psychological Science. (ANI)